I've got a few questions regarding the subject line:

I'm changing the front diff lube and installing a 75W-90 Synthetic EP Lubricant on my 2002 4WD Navigator with 95k on the clock.

1st question: What a time I had getting the fill and drain plugs out of the diff! (Can't swing a 42" breaker bar with the vehicle on the ground. ) Looks like someone used red loctite (or equivalent) to install these plugs. Is this a good idea when I reinstall the plugs?

2nd question: The lube looked clean and clear so maybe it has been changed before. (I know that the lube has at least 27k on it.) But the drain plug had about 1/4" of gray paste stuck to the magnet. Is this typical?

3rd Question: I know Ford specifies that the rear diff be filled to ~3/8" below the fill hole, but can't find a spec for the front diff. It was about 1/2" below the fill hole before I drained it. Does anyone know what the correct fill level of the front diff is?

Thank You in advance for any and all responses........................

 

Wow, with synthetic the orginal fluid, I wouldn't have change it. But since your rambunctuous, the standard I've used is about a 1/2" below. I use the 'ol backwoods method of a finger tip below the plug.

 

I didn't realize the front diff came from the factory filled with synthetic lube, but I knew the rear diff did.

Just found the Ford spec for the front diff lubricant: "Motorcraft SAE 75W-90 Premium 4X4 Front Axle Lubricant XY-75W90-TQL" or equivalent meeting Ford specification WSP-M2C201-A. Must be something in those numbers indicates Synthetic -

And it did specify the lube level at .38" below the bottom of the fill hole.

I think I'm gonna go with ye 'ol backwoods method.

 

I still have the bottle at home from when I changed my fluid as well. I'll go home and see how much I put in and post my results. I know I found the exact amounts somewhere or a guide but can't see to find it. I'll get back in touch...

Edit: Out of a 30 oz bottle of fluid, I had 10 oz remaining so the front differential requires around 20 oz of oil.

 

Thanks for checking.

I did find the capacity spec for the 2002 Navigator front diff. It takes 3.8 pints of 75W-90 lubricant. I had 2 quarts (= 4 pints or 64 ounces). When I had the diff filled to within ~1/4" of the bottom of the fill hole, I had `6 oz of lube left over.

I didn't think the old lube was very dirty as it drained out of the diff, but afterwards I poured some of it in the empty quart bottle to compare to the new lube. If I can make a picture post, you'll be able to see how dirty it was and how much gear oil was left over.

https://www.ford-trucks.com/forums/p...ictureid=72157

 

Ford shop manual indicates the front diff fluid for that year was not synthetic. You also fill the diffs until fluid starts to come out the fill plug hole.

 

Really?....it was my understanding in order to keep the fluid temp down and fluid break down to a minimum that all diffs since '96 came with synthetic? That way they didn't have to do what Nissan did and put on those more expensive heat disapater covers and hope it worked.

 

No read the manual.Rear diffs are synthetic , part time 4wd front axles are non synthetic.

 

My Ford Motor Company Service Manual shows the lube level of the front diff to be 9.56mm (0.38") below the fill hole.

Perhaps they mean that is the lowest allowed level?

 

That's only about a 1/4", so I would decipher that as minimum suggested level. Some folks say to fill it 'til it runs out the plug. In any case a 1/4" more won't kill anything.

 

To be exact: 3.5-3.7 pints according to the owner's manual.